sql server数据库的原始查询数据，并返回结果

  //调整使用占位符进行处理，时间：2017/9/29                    string strql = @"select * from SYS_User where  username=@username and userpwd=@userpwd ";

                   //创建连接对象                    SqlConnection con = new SqlConnection(strco);

                   SqlDataAdapter da = new SqlDataAdapter(strql, con);

                   //命令                    SqlCommand cmd = da.SelectCommand;

                   cmd.CommandType = CommandType.Text;

                   //sql传参的绑定                    cmd.Parameters.Add(new SqlParameter("@username", txt_UserName.Text));

                   cmd.Parameters.Add(new SqlParameter("@userpwd", txt_Pwd.Text));

                   DataSet ds = new DataSet();

                   da.Fill(ds, "info");

                   DataTable dt = ds.Tables[0];